computer notes - standard template library

Standard Template Library

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Standard Template Library

• C++ programmers commonly use many data

structures and algorithms

• So C++ standard committee added the STL to

C++ standard library

• STL is designed to operate efficiently across

many different applications


…Standard Template Library

• STL consists of three key components

– Containers

– Iterators

– Algorithms


STL Promotes Reuse

• Software reuse saves development time and

cost

• Once tested component can be reused

several times


STL Containers

• Container is an object that contains a

collection of data elements

• STL provides three kinds of containers

– Sequence Containers

– Associative Containers

– Container Adapters


Sequence Containers

• A sequence organizes a finite set of objects,

all of the same type, into a strictly linear

arrangement


…Sequence Containers

• vector

– Rapid insertions and deletions at back end

– Random access to elements

• deque

– Rapid insertions and deletions at front or back

– Random access to elements

• list

– Doubly linked list

– Rapid insertions and deletions anywhere


Example – STL Vector

#include <vector>

int main() {

std::vector< int > iv;

int x, y;

char ch;

do {

cout<<"Enter the first integer:";

cin >> x;

cout<<"Enter the second integer:";

cin >> y;http://ecomputernotes.com

…Example – STL Vector

iv.push_back( x );

iv.push_back( y );

cout << “Current capacity of iv = “ << iv.capacity() << endl;

cout << “Current size of iv =“

<< iv.size() << endl;

cout<<"Do you want to continue?";

cin >> ch;

} while ( ch == 'y' );

}http://ecomputernotes.com

Sample Output

Enter the first integer: 1

Enter the second integer: 2

Current capacity of iv = 2

Current size of iv = 2

Do you want to continue? y


…Sample Output





Do you want to continue? y


…Sample Output





Do you want to continue? n


Example – STL Deque

#include <deque>

int main() {

std::deque< int > dq;

dq.push_front( 3 );

dq.push_back( 5 );

dq.pop_front();

dq.pop_back()

return 0;

} http://ecomputernotes.com

Example – STL List

#include <list>

int main() {

std::list< float > _list;

_list.push_back( 7.8 );

_list.push_back( 8.9 );

std::list< float >::iterator it

= _list.begin();

_list.insert( ++it, 5.3 );

return 0;


Associative Containers

• An associative container provide fast retrieval

of data based on keys


…Associative Containers

• set

– No duplicates

• multiset

– Duplicates allowed

• map

– No duplicate keys

• multimap

– Duplicate keys allowed


Example – STL Set

#include <set>

int main() {

std::set< char > cs;

cout << “Size before insertions: “<< cs.size() << endl;

cs.insert( ‘a’ );

cs.insert( ‘b' );

cs.insert( ‘b' );

cout << “Size after insertions: ”

<< cs.size();

return 0;


Output

Size before insertions: 0

Size after insertions: 2


Example – STL Multi-Set

#include <set>

int main() {

std::multiset< char > cms;

cout << "Size before insertions: " << cms.size() << endl;

cms.insert( 'a' );

cms.insert( 'b' );

cms.insert( 'b' );

cout << "Size after insertions: "

<< cms.size();

return 0;


Output

Size before insertions: 0

Size after insertions: 3


Example – STL Map

#include <map>

int main() {

typedef std::map< int, char > MyMap;

MyMap m;

m.insert(MyMap::value_type(1, 'a'));

m.insert(MyMap::value_type(2, 'b'));

m.insert(MyMap::value_type(3, 'c'));

MyMap::iterator it = m.find( 2 );

cout << "Value @ key " << it->first << " is " << it->second;

return 0;


Output

Value @ key 2 is b


Example – STL Multi-Map

#include <map>

int main() {

typedef std::multimap< int, char > MyMap;

MyMap m;

m.insert(MyMap::value_type(1, 'a'));

m.insert(MyMap::value_type(2, 'b'));

m.insert(MyMap::value_type(3, 'b'));http://ecomputernotes.com

…Example – STL Multi-Map

MyMap::iterator it1 = m.find( 2 );

MyMap::iterator it2 = m.find( 3 );

cout << "Value @ key " << it1->first << " is " << it1->second << endl;

cout << "Value @ key " << it2->first << " is " << it2->second << endl;

return 0;

}


Output

Value @ key 2 is b

Value @ key 3 is b


First-class Containers

• Sequence and associative containers are

collectively referred to as the first-class

containers


Container Adapters

• A container adapter is a constrained version of

some first-class container


…Container Adapters

• stack

– Last in first out (LIFO)

– Can adapt vector, deque or list

• queue

– First in first out ( FIFO)

– Can adapt deque or list

• priority_queue

– Always returns element with highest priority

– Can adapt vector or deque


Common Functions for All

Containers

• Default constructor

• Copy Constructor

• Destructor

• empty()

– Returns true if container contains no elements

• max_size()

– Returns the maximum number of elements


…Common Functions for All

Containers

• size()

– Return current number of elements

• operator = ()

– Assigns one container instance to another

• operator < ()

– Returns true if the first container is less than the

second container



Containers

• operator <= ()

– Returns true if the first container is less than or equal to the second container

• operator > ()

– Returns true if the first container is greater than the second container

• operator >= ()

– Returns true if the first container is greater than or equal to the second container



Containers

• operator == ()

– Returns true if the first container is equal to the second container

• operator != ()

– Returns true if the first container is not equal to the second container

• swap ()

– swaps the elements of the two containers


Functions for First-class

Containers

• begin()

– Returns an iterator object that refers to the first

element of the container

• end()

– Returns an iterator object that refers to the

next position beyond the last element of the

container


…Functions for First-class

Containers

• rbegin()

– Returns an iterator object that refers to the last

element of the container

• rend()

– Returns an iterator object that refers to the position before the first element



Containers

• erase( iterator )– Removes an element pointed to by the iterator

• erase( iterator, iterator )

– Removes the range of elements specified by the first and the second iterator parameters



Containers

• clear()

– erases all elements from the container


Container Requirements

• Each container requires element type to

provide a minimum set of functionality e.g.

• When an element is inserted into a container,

a copy of that element is made

– Copy Constructor

– Assignment Operator


…Container Requirements

• Associative containers and many algorithms

compare elements

– Operator ==

– Operator <


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